1. Field of the Disclosure
The present invention relates to an electronic device based on materials of the group III/N, such as a rectifier or a field effect transistor, for example of the HEMT type (High Electron Mobility Transistor) or of the MIS type (Metal Insulator Semiconductor).
2. Description of Related Art
The materials of the group III/N such as GaN for example, have piezo-electrical properties.
In an electronic device based on materials of the group III/N, a spontaneous polarization exists which creates an electrical field that is inherent to the non centro-symmetrical crystallographic structure of the material. Moreover, another piezo-electrical field is also induced by the different stresses present in the different layers of the structure. This electrical field of a piezo-electrical nature is substantially constant on the surface of the device, as long as it is not modified by etching, for example.
However, to improve the performance of electronic devices, it would be preferable to be able to control the distribution of the electrical field on the surface of the device, which is to say to be able to create, with a precise spatial resolution, regions on the surface of the device where the electrical field is weak, and other regions where the electrical field is strong.
In reference to FIG. 1, the type of electronic device that the invention intends to improve typically comprises from its base towards its surface: a support layer 1, a buffer layer 2, a channel layer 3, a barrier layer 4 and a superficial layer 7. This device may also comprise an ohmic contact electrode 5 and a Schottky contact electrode 8.
By the surface of the device, it is meant the upper layer of the device—in this case, the superficial layer 7, onto which electrodes may be deposited. This surface may be flat or not (for example if it has been etched).
In order to make the following description easier to understand, an orthogonal reference (x, y, z) system is defined that is attached to the device. The x and y directions define a horizontal plane, parallel to the base of the device, the z direction is vertical and is perpendicular to this plane. This reference will be conserved throughout the description.
In general, when seeking to optimize the performances of such an electronic device, it is the structure and the electrical field of the latter that are sought to be optimized in its z axis, which is to say by improving the structure along its thickness. The present disclosure provides improved methods and structures that address deficiencies in the art.